The present invention generally relates to a rotating disk storage device and an integrated wire head suspension assembly. The invention relates more particularly to an integrated wire head suspension assembly that can improve upon an inconvenience involved in bonding a lead wiring pad provided on an end portion of a lead of the head suspension assembly to a bonding pad provided in a slider of the head suspension assembly, and a rotating disk storage device that uses the integrated wire head suspension assembly.
With hard disk devices becoming smaller and smaller these years, requirements have become even more stringent for design and manufacture of different parts of suspensions that move magnetic heads. Connecting a lead to a slider having a magnetic head, in particular, has become an extremely difficult job to perform. In addition, the weight of the lead itself, a lead wiring position, and the like have come to affect head control. An integrated wire suspension, which suppresses variations caused by wiring through bonding a wire portion on the suspension or forming a wire pattern thereon, is now known.
In the integrated wire suspension, it is necessary to connect a lead wiring pad provided on a flexure portion on the suspension side with a bonding pad provided on the slider. The connection surface between the lead wiring pad and the bonding pad is such that planes formed by extending the two pads are perpendicular to each other (that is, a virtual right angle is formed at an intersection point of the two planes as viewed from a side). Various new techniques are employed, since a technique used for connecting ordinary opposing surfaces is not effective in connecting the two surfaces running at right angles to each other.
One known technique used for joining the lead wiring pad with the bonding pad, each having an orthogonal positional relation with each other, is, for example, apple bonding that uses a gold (Au) ball. In apple bonding, a gold ball is pressed against the virtual right angle formed between the lead wiring pad and the bonding pad. The gold ball is then subjected to ultrasonic welding to make a connection between the two pads. Another technique, for example, a technique using a solder ball, is disclosed (see, for example, Japanese Patent Laid-Open No. 2003-123217).
The technique using the solder ball proceeds as follows. Specifically, the integrated wire suspension is supported so that the virtual right angle formed by the two pads faces upward in a vertical direction. The solder ball is then disposed between the two pads. The solder ball is thereafter irradiated with a laser beam, which melts the solder so as to form a soldered connection between the two pads.
FIG. 13 shows how the lead wiring pad and the bonding pad are joined together using the solder ball in a conventional integrated wire suspension.
A flexure 101 of the suspension is of a dual-layer structure including a polyimide layer 102 of a high polymeric material having insulating properties and a stainless steel foil layer 103. Leads 104 are formed as a conductor layer on top of the polyimide layer 102. Lead wiring pads 105 are formed on distal ends of the leads 104. The lead wiring pads 105 are formed to have a wider width than the leads 104 do to provide sufficient areas for solder connections.
The polyimide layer 102 and the stainless steel foil layer 103 can be formed into corresponding desired shapes by, for example, etching the layers after required portions have been covered with a resist. If the polyimide layer 102 is a photosensitive polyimide layer, required portions of the photosensitive polyimide layer 102 are covered with a resist or the like before the layer is subjected to exposure and developing processes. The photosensitive polyimide layer 102 can then be formed into a desired shape.
An opening portion 106 is formed on leading end portions of the lead wiring pads 105 in the flexure 101. This is done to prevent an excess adhesive from sticking to the lead wiring pads 105 when the slider is bonded to the suspension. Or, the opening portion 106 is provided to prevent the high polymer polyimide layer 102 from being changed by heat generated through radiation of the laser beam. The leading end portions of the lead wiring pads 105 are therefore aerially wired, protruding in the opening portion 106. U-shaped cutout portions 107 are formed in the lead wiring pads 105. The cutout portion 107 lets a solder ball 200 fall from a front surface of the lead wiring pad 105 onto an area near a centerline of the front surface of the lead wiring pad 105 by gravity.
A slider 108 having a hard disk magnetic head built therein is mounted to the flexure 101. As described in the foregoing, bonding pads 109 of the slider 108 are disposed at positions perpendicular to the lead wiring pads 105. This means that a plane formed by extending a surface of the bonding pad 109 crosses a plane formed by extending a surface of the lead wiring pad 105. Virtual axes that run at right angles to each other therefore form 90 degrees (right angle) at the intersection point.
When the bonding pad 109 and the lead wiring pad 105 are connected with the solder ball 200, the suspension (flexure 101) is secured so that the virtual right angle formed by the bonding pad 109 and the lead wiring pad 105 opens to face upward in the vertical direction. The flexure 101 is usually secured in position as follows. Specifically, the lead wiring pad 105 on the flexure 101 and the bonding pad 109 on the slider 108 rise in a direction of 45 degrees from a horizontal plane, while each maintaining an orthogonal positional relation with each other. A solder ball loading device (not shown) is then used to drop the solder ball 200 onto an area between the two pads that have been secured in position. The solder ball 200 is then heated and melted using a laser beam radiation device (not shown) to make a soldered joint between the two pads.
The conventional integrated wire suspension employed the steps as described in the foregoing to connect the bonding pad 109 with the lead wiring pad 105 using the solder ball 200.
The integrated wire suspensions are available in the following three types according to a manufacturing method employed. In any of the manufacturing methods, the steps as described in the foregoing are followed to connect the bonding pad 109 with the lead wiring pad 105 using the solder ball 200. The three types are:
(a) An additive type, in which copper foil wires and pads are added on an insulator of the suspension;
(b) A subtractive type, in which wires and pads are formed by etching a copper foil formed in a sheet on the insulator of the suspension; and
(c) An FPC type, in which a flexible printed circuit board (FPC), on which copper foil wires and pads are formed, is bonded to the suspension.